Valence Electrons l The electrons responsible for the chemical properties of atoms are those in the outer energy level. l Valence electrons - The electrons.

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Presentation on theme: "Valence Electrons l The electrons responsible for the chemical properties of atoms are those in the outer energy level. l Valence electrons - The electrons."— Presentation transcript:

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Keeping Track of Electrons l Atoms in the same column... –Have the same outer electron configuration. –Have the same valence electrons. l Easily found: same as the main group number on the periodic table. l Group 2: Be, Mg, Ca, Sr, Ba. –2 valence electrons

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Electron Dot diagrams l A way of keeping track of valence electrons. l How to write them? l Write the symbol. l Put one dot for each valence electron l Don’t pair up until they have to. X

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The Electron Dot diagram for Nitrogen l Nitrogen has 5 valence electrons. l First we write the symbol. N l Then add 1 electron at a time to each side. l Until they are forced to pair up.

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Ionic Bonding  Between metals and non-metals  Transfer of electrons  Full outer shells  Oppositely charged ions created  Ions held to one another by electrostatic attraction  Giant structure formed

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Ionic Bonds Characteristics of ionic compounds l Usually soluble in water l Electrical conductors when molten and when in aqueous solution. l High m.p. l Brittle, hard crystals

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Ionic Bonding l Anions and cations are held together by opposite charges. l Ionic compounds are called salts. l Simplest ratio is called the formula unit. l The bond is formed through the transfer of electrons. l Electrons are transferred to achieve noble gas configuration.

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Ionic Bonding NaCl

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Ionic Bonding Na + Cl -

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Ionic Bonding l All the electrons must be accounted for CaP

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Ionic Bonding CaP

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Ionic Bonding Ca 2+ P

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Ionic Bonding Ca 2+ P Ca

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Ionic Bonding Ca 2+ P 3- Ca

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Ionic Bonding Ca 2+ P 3- Ca P

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Ionic Bonding Ca 2+ P 3- Ca 2+ P

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Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

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Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

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Ionic Bonding Ca 2+ P 3- Ca 2+ P 3- Ca 2+

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Ionic Bonding = Ca 3 P 2 Formula Unit Calcium Phosphide

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Classwork problems (a) Show the bonding between the following 1. Magnesium and Oxygen 2. Potassium and Chlorine 3. Calcium and Fluorine 4. Lithium and Nitrogen 5. Aluminium and Fluorine

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Conducting electricity l Conducting electricity is allowing charges to move. l In a solid, the ions have charges but are locked in place. l Ionic solids are insulators. l When melted, the charged ions can move around. Melted ionic compounds conduct electricity. –To melt NaCl, it must get to about 800 ºC. l Dissolved in water (aqueous) the ions are now free to move and they conduct electricity.

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Ionic solids are brittle

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l Displacing the top layer (diagram) puts ions of the same charge near one another creating strong repulsion that breaks the crystal apart.

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Solubility l Ionic solids are often (but not always) soluble in water. l Solubility usually (but not always) increases with increasing temperature.